Im getting the magnaflow w x pipe kit from NPD and I dont know which size to go with the 2.5 inch or 3.0.

Its a stock 289 now with a 600 cfm holley upgrade. I plan on getting heads and strokeing it to 347. I dont wanna hold up my exaust system down the road, will 2.5 be enough for a 347 or will it hold it back?

 

2.5 is more than enough for that set-up.

 

2.5in will be plenty. I think 3in will hurt you because you will have no back pressure.

 

2.5 sounds awesome, thats what i have on mine! sounds great!

 

2.25" would be enough.

 

2.5 is fine....you could always compromise and get 3" entry pipe to an X with 2.5" exiting pipe (since most header collectors are 3"). At any rate, 2.5" is fine.

 

i wouldnt go over that 2.5 unless your running a turbo

 

or nitrous

 

mojoe that depends the shot size

 

at 150, having at least the front section of the midpipe up to the x at 3" definitely helps....trust me